With an increase in the packing density of LSIs, the required linewidths of circuits included in semiconductor devices become finer year by year. To form a desired circuit pattern on a semiconductor device, a method is employed in which a high-precision original pattern (i.e., a mask, or also particularly called reticle, which is used in a stepper or a scanner) formed on quartz is transferred to a wafer in a reduced manner by using a reduced-projection exposure apparatus. The high-precision original pattern is drawn by using an electron-beam drawing apparatus, in which a so-called electron-beam lithography technique is employed.
A drawing apparatus using multi-beam can emit more beams at a time than in a case of drawing with a single electron beam and can greatly improve throughput. In such a multi-beam drawing apparatus, for example, an electron beam emitted from an electron gun is passed through an aperture member having a plurality of holes, whereby multiple beams (a plurality of electron beams) are formed. The multiple beams pass through respective blankers provided in a blanking plate. The blankers individually perform blanking deflection on the electron beams passing therethrough. Some electron beams that have been deflected by the blankers are blocked by the blankers, while the other electron beams that have not been deflected fall onto a sample.
Each of the beams forming the multi-beam has a small size. To improve throughput, many beams are necessary and the blanking plate needs to mount wiring lines and circuits for independently controlling the potentials of electrodes of the blankers. Data that defines the on or off state of each of the beams is transferred to the blanking plate. The amount of data transferred to the blanking plate is far greater than the amount of data required in a case of drawing with a single electron beam.
The blanking plate is die-bonded to a mounting substrate. The mounting substrate is provided with a circuit device for power stabilization, a control circuit, a relay circuit for data transfer, and so forth. A column of a drawing apparatus in which the mounting substrate mounting the blanking plate is disposed has a vacuum thereinside and has a low rate of heat exhaustion. Therefore, the above circuit devices may fail to be cooled satisfactorily and may become hot, generating some gas. Moreover, if the circuit devices are made of any materials that generate gas in a vacuum, such gas may be generated from the circuit devices in the vacuum column. If any gas is generated in the column, the aperture member may be contaminated and the holes for forming multiple beams may be clogged. In addition, if the circuit devices become hot, the circuit devices may cause malfunctions.
In another case, electrons scattered at the aperture member may charge up the surface or inside of the circuit devices on the mounting substrate and may cause malfunctions. In yet another case, an electromagnetic field generated by the electric current flowing through the circuit devices and the mounting substrate may disturb the paths of the electron beams and may deteriorate the drawing accuracy.